Serotonin Syndrome, also known as malignant carcinoid syndrome, is related to neuroleptic malignant syndrome and headache. An important gene associated with Serotonin Syndrome is HTR3A (5-Hydroxytryptamine Receptor 3A), and among its related pathways/superpathways are Signal Transduction and GPCR downstream signalling. The drugs Octreotide and Gastrointestinal Agents have been mentioned in the context of this disorder. Affiliated tissues include heart and kidney, and related phenotypes are abnormality of the autonomic nervous system and tremor